For historical reasons, the standard QWERTY keyboard which was developed for mechanical typewriters the most common medium for inputting information to a computer. The size and spacing of the keys on such a keyboard was determined by the size of the human hand and fingers. For each key to be strongly struck a travel motion of at least 3/16" was required. The letter or symbol associated with a given key was determined by the frequency of occurrence of the different letters in the English language. Personal computers continue to use electronic equivalents of the mechanical QWERTY keyboard. Personal computers have been progressively miniaturized, so that presently pocket computers, or "palm top" computers (also referred to as "personal digital assistants") are available which are foldable to fit in the user's pocket. An example is the CASIO PEIA.TM. personal digital assistant. Operating systems are provided for such palm top computers such as WINDOWS/95 CE.TM. which allow the user to run applications software designed for personal computers. However in order to fit a keyboard into a palm top computer, the existing solution has been to miniaturze the keys of the keyboard. This makes it impossible for the user to type on the keyboard in the usual way. The screens also are very small.
U.S. Pat. No. 3,940,758, issued Feb. 24, 1976 to Margolin, discloses an expandable keyboard for a pocket calculator, in which the keyboard pad is formed of three modular sections which are hinged together mechanically, normally forming a stack which spreads into an enlarged keyboard. However the enlarged keyboard in Margolin is still considerably smaller than a standard keyboard (the two expansion sections bring 6.5 inches wide, compared to about 11 inches for a standard keyboard), and therefore use of the device for current word processing applications was clearly not contemplated, nor would calculators of that era have had the computing power and software for such uses.
A number of patents disclose hinged extensions to expand the keyboard of a notebook computer. For example, U.S. Pat. No. 5,187,644 issued Feb. 16, 1993 and U.S. Pat. No. 5,519,569 issued May 21, 1996, both to Compaq Computer Corp. disclose portable computers of the notebook variety having extendable end segments which are hinged to the central keyboard. U.S. Pat. No. 5,457,453 issued Oct. 10, 1995 discloses a miniature computer having a folding keyboard, which leaves a jagged edge when folded. However none of these devices provide a full size keyboard for a folding pocket computer.
There is therefore a need for a folding miniaturized computer, to allow the keyboard and screen to fit into a person's pocket, which nonetheless provides a full size keyboard and a useful screen when opened.